My 15 year old has had this for the past few years. She even used it last time she flew to skip a long line that the rest of us had to stand in.
I've always wondered if someone incorrectly checked off some wrong box sometime to accidentally give her this access?
My husband and I are applying for this access ourselves now. We should probably also get it for our 12 year old so all 4 of us have it. That said, my 15yo doesn't have a card to go with her Pre-Check boarding passes, and I guess they could request the card any time she uses the Nexus lines?